Safety methods for use in power equipment

ABSTRACT

Woodworking machines and safety methods for use with those machines are disclosed. The machines include a detection system adapted to detect one or more dangerous conditions and a reaction system associated with the detection system. The reaction system can include an explosive to trigger the system, and also can be configured to retract a cutting tool at least partially away from a cutting region upon detection of a dangerous condition by the detection system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of the following U.S. patentapplications, all of which are hereby incorporated by reference in theirentireties for all purposes:

Ser. No. 09/929,426, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,200, filed Aug. 14, 2000;

Ser. No. 09/929,221, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,211, filed Aug. 14, 2000;

Ser. No. 09/929,227, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,170, filed Aug. 14, 2000;

Ser. No. 11/401,050, filed Apr. 10, 2006, which is a continuation of anumber of applications including Ser. No. 09/929,241, filed Aug. 13,2001, issuing as U.S. Pat. No. 7,024,975 on Apr. 11, 2006, which in turnclaimed the benefit of and priority from a number of U.S. ProvisionalPatent Applications including Ser. No. 60/225,169, filed Aug. 14, 2000;

Ser. No. 09/929,242, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,089, filed Aug. 14, 2000;

Ser. No. 10/984,643, filed Nov. 8, 2004, which is a continuation of anumber of applications, including Ser. No. 10/205,164, filed Jul. 25,2002, issuing as U.S. Pat. No. 6,945,149 on Sep. 20, 2005, which in turnclaimed the benefit of and priority from U.S. Provisional PatentApplication Ser. No. 60/307,756, filed Jul. 25, 2001, and Ser. No.10/202,928, filed Jul. 25, 2002, issuing as U.S. Pat. No. 7,000,514 onFeb. 21, 2006, which in turn claimed the benefit of and priority fromU.S. Provisional Patent Application Ser. No. 60/308,492, filed Jul. 27,2001;

Ser. No. 09/929,236, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,201, filed Aug. 14, 2000;

Ser. No. 11/061,162, filed Feb. 18, 2005, which is a continuation ofSer. No. 09/929,244, filed Aug. 13, 2001, issuing as U.S. Pat. No.6,857,345 on Feb. 22, 2005, which in turn claimed the benefit of andpriority from a number of U.S. Provisional Patent Applications includingSer. No. 60/225,212, filed Aug. 14, 2000;

Ser. No. 09/929,237, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,059, filed Aug. 14, 2000;

Ser. No. 09/929,234, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,094, filed Aug. 14, 2000;

Ser. No. 09/929,425, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,210, filed Aug. 14, 2000;

Ser. No. 11/190,111, filed Jul. 25, 2005, which is a continuation of anumber of applications including Ser. No. 09/929,226, filed Aug. 13,2001, issuing as U.S. Pat. No. 6,920,814 on Jul. 26, 2005, which in turnclaimed the benefit of and priority from a number of U.S. ProvisionalPatent Applications including Ser. No. 60/225,206, filed Aug. 14, 2000;Ser. No. 10/205,164, filed Jul. 25, 2002, issuing as U.S. Pat. No.6,945,149 on Sep. 20, 2005, which in turn claimed the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/307,756,filed Jul. 25, 2001; and Ser. No. 10/202,928, filed Jul. 25, 2002,issuing as U.S. Pat. No. 7,000,514 on Feb. 21, 2006, which in turnclaimed the benefit of and priority from U.S. Provisional PatentApplication Ser. No. 60/308,492, filed Jul. 27, 2001;

Ser. No. 09/929,235, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,058, filed Aug. 14, 2000;

Ser. No. 09/929,238, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,057, filed Aug. 14, 2000;

Ser. No. 11/447,449, filed Jun. 5, 2006, which is a continuation of Ser.No. 09/676,190, filed Sep. 29, 2000, issuing as U.S. Pat. No. 7,055,417on Jun. 6, 2006, which in turn claimed the benefit of and priority fromthe following U.S. Provisional Patent Applications: Ser. No. 60/182,866,filed Feb. 16, 2000, and Ser. No. 60/157,340, filed Oct. 1, 1999;

Ser. No. 10/053,390, filed Jan. 16, 2002, which is acontinuation-in-part of a number of applications including Ser. No.09/676,190, filed Sep. 29, 2000, issuing as U.S. Pat. No. 7,055,417 onJun. 6, 2006; and Ser. No. 10/053,390 also claims the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/270,011,filed Feb. 20, 2001;

Ser. No. 11/348,580, filed Feb. 6, 2006, which is a continuation of anumber of applications including Ser. No. 10/052,705, filed Jan. 16,2002, issuing as U.S. Pat. No. 6,994,004 on Feb. 7, 2006, which in turnclaimed the benefit of and priority from the following U.S. ProvisionalPatent Applications: Ser. No. 60/270,011, filed Feb. 20, 2001, Ser. No.60/270,941, filed Feb. 22, 2001, Ser. No. 60/270,942, filed Feb. 22,2001, Ser. No. 60/273,177, filed Mar. 2, 2001, and Ser. No. 60/273,178,filed Mar. 2, 2001; and Ser. No. 11/348,580 also claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/667,485, filed Mar. 31, 2005;

Ser. No. 10/932,339, filed Sep. 1, 2004, which is a continuation of Ser.No. 10/047,066, filed Jan. 14, 2002, issuing as U.S. Pat. No. 6,945,148on Sep. 20, 2005, which in turn claimed the benefit of and priority fromthe following U.S. Provisional Patent Applications: Ser. No. 60/270,011,filed Feb. 20, 2001, Ser. No. 60/270,941, filed Feb. 22, 2001, Ser. No.60/270,942, filed Feb. 22, 2001, Ser. No. 60/273,177, filed Mar. 2,2001, Ser. No. 60/273,178, filed Mar. 2, 2001, and Ser. No. 60/273,902,filed Mar. 6, 2001; and Ser. No. 10/392,339 is also a continuation ofSer. No. 10/050,085, filed Jan. 14, 2002;

Ser. No. 10/100,211, filed Mar. 13, 2002, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/275,583, filed Mar. 13, 2001;

Ser. No. 11/256,757, filed Oct. 24, 2005, which is a continuation ofSer. No. 09/955,418, filed Sep. 17, 2001, issuing as U.S. Pat. No.6,957,601 on Oct. 25, 2005, which in turn claimed the benefit of andpriority to a number of U.S. Provisional Patent Applications, including:Ser. No. 60/233,459, filed Sep. 18, 2000, Ser. No. 60/270,011, filedFeb. 20, 2001, Ser. No. 60/270,941, filed Feb. 22, 2001, Ser. No.60/270,942, filed Feb. 22, 2001, Ser. No. 60/273,177, filed Mar. 2,2001, Ser. No. 60/273,178, filed Mar. 2, 2001, Ser. No. 60/273,902,filed Mar. 6, 2001, Ser. No. 60/275,594, filed Mar. 13, 2001, Ser. No.60/275,595, filed Mar. 13, 2001, Ser. No. 60/279,313, filed Mar. 27,2001, Ser. No. 60/292,081, filed May 17, 2001, Ser. No. 60/292,100,filed May 17, 2001, Ser. No. 60/298,207, filed Jun. 13, 2001, Ser. No.60/302,937, filed Jul. 2, 2001, Ser. No. 60/302,916, filed Jul. 3, 2001,Ser. No. 60/306,202, filed Jul. 18, 2001, Ser. No. 60/307,657, filedJul. 25, 2001, Ser. No. 60/308,492, filed Jul. 27, 2001, and Ser. No.60/312,141, filed Aug. 13, 2001;

Ser. No. 10/146,527, filed May 15, 2002, which claims the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/292,100,filed May 17, 2001;

Ser. No. 11/218,356, filed Sep. 2, 2005, which is a continuation of anumber of applications including Ser. No. 10/146,527, filed May 15,2002, which in turn claims the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/292,100, filed May 17, 2001;

Ser. No. 10/172,553, filed Jun. 13, 2002, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/298,207, filed Jun. 13, 2001;

Ser. No. 10/189,031, filed Jul. 2, 2002, which claims the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/302,937,filed Jul. 2, 2001;

Ser. No. 10/189,027, filed Jul. 2, 2002, which claims the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/302,916,filed Jul. 3, 2001;

Ser. No. 11/353,423, filed Feb. 13, 2006, which is a continuation ofSer. No. 10/785,361, filed Feb. 23, 2004, issuing as U.S. Pat. No.6,997,090 on Feb. 14, 2006, which in turn is a continuation of Ser. No.10/215,929, filed Aug. 9, 2002, which in turn claimed the benefit of andpriority to U.S. Provisional Patent Application Ser. No. 60/312,141,filed Aug. 13, 2001;

Ser. No. 11/208,214, filed Aug. 19, 2005, which is a continuation ofSer. No. 10/251,576, filed Sep. 20, 2002, which in turn was acontinuation-in-part of Ser. No. 10/197,975, filed Jul. 18, 2002, andwhich claimed the benefit of and priority to U.S. Provisional PatentApplication Ser. No. 60/323,975, filed Sep. 21, 2001, and Ser. No.11/208,214 is also a continuation-in-part of Ser. No. 09/676,190, filedSep. 29, 2000, issuing as U.S. Pat. No. 7,055,417 on Jun. 6, 2006, whichin turn claimed the benefit of and priority from U.S. Provisional PatentApplication Ser. No. 60/157,340, filed Oct. 1, 1999 and Ser. No.60/182,866, filed Feb. 16, 2000;

Ser. No. 10/243,042, filed Sep. 13, 2002, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/324,729, filed Sep. 24, 2001;

Ser. No. 11/487,717, filed Jul. 17, 2006, which is a continuation ofSer. No. 10/292,607, filed Nov. 12, 2002, issuing as U.S. Pat. No.7,077,039 on Jul. 18, 2006, which in turn claimed the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/335,970,filed Nov. 13, 2001;

Ser. No. 10/345,630, filed Jan. 15, 2003, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/349,989, filed Jan. 16, 2002;

Ser. No. 10/341,260, filed Jan. 13, 2003, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/351,797, filed Jan. 25, 2002;

Ser. No. 11/445,548, filed Jun. 2, 2006, which is a continuation of anumber of applications, including the following: Ser. No. 09/929,240,filed Aug. 13, 2001, issuing as U.S. Pat. No. 7,100,483 on Sep. 5, 2006,which in turn claimed the benefit of and priority from a number of U.S.Provisional Patent Applications including Ser. No. 60/225,056, filedAug. 14, 2000; Ser. No. 10/643,296, filed Aug. 18, 2003, which in turnclaimed the benefit of and priority from U.S. Provisional PatentApplication Ser. No. 60/406,138, filed Aug. 27, 2002; and Ser. No.10/794,161, filed Mar. 4, 2004, issuing as U.S. Pat. No. 7,098,800 onAug. 29, 2006, which in turn claimed the benefit of and priority fromU.S. Provisional Patent Application Ser. No. 60/452,159, filed Mar. 5,2003;

Ser. No. 10/923,290, filed Aug. 20, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/496,550, filed Aug. 20, 2003;

Ser. No. 10/923,273, filed Aug. 20, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/496,574, filed Aug. 20, 2003;

Ser. No. 11/401,774, filed Apr. 11, 2006, which is a continuation of anumber of applications including Ser. No. 11/027,322, filed Dec. 31,2004, which in turn claimed the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/533,598, filed Dec. 31, 2003;and Ser. No. 11/401,774 is also a continuation of Ser. No. 09/676,190,filed Sep. 29, 2000, issuing as U.S. Pat. No. 7,055,417 on Jun. 6, 2006,which in turn claimed the benefit of and priority from U.S. ProvisionalPatent Application Ser. No. 60/157,340, filed Oct. 1, 1999 and Ser. No.60/182,866, filed Feb. 16, 2000;

Ser. No. 11/506,260, filed Aug. 18, 2006, which is a continuation of anumber of application including Ser. No. 10/923,282, filed Aug. 20,2004, which in turn claimed the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/496,568, filed Aug. 20, 2003;

Ser. No. 11/027,600, filed Dec. 31, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/533,791, filed Dec. 31, 2003;

Ser. No. 11/107,499, filed Apr. 15, 2005;

Ser. No. 11/027,254, filed Dec. 31, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/533,852, filed Dec. 31, 2003;

Ser. No. 11/026,114, filed Dec. 31, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/533,811, filed Dec. 31, 2003;

Ser. No. 11/026,006, filed Dec. 31, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/533,575, filed Dec. 31, 2003;

Ser. No. 11/045,972, filed Jan. 28, 2005, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/540,377, filed Jan. 29, 2004;

Ser. No. 11/395,502, filed Mar. 31, 2006, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/667,485, filed Mar. 31, 2005; and

Ser. No. 11/098,984, filed Apr. 4, 2005, which is a continuation of aSer. No. 09/929,238, filed Aug. 13, 2001, Ser. No. 10/047,066, filedJan. 14, 2002, issuing as U.S. Pat. No. 6,945,148 on Sep. 20, 2005, Ser.No. 10/051,782, filed Jan. 15, 2002, issuing as U.S. Pat. No. 6,877,410on Apr. 12, 2005, which in turn claimed the benefit of and priority fromthe following U.S. Provisional Patent Applications: Ser. No. 60/270,011,filed Feb. 20, 2001, Ser. No. 60/270,941, filed Feb. 22, 2001, Ser. No.60/270,942, filed Feb. 22, 2001, Ser. No. 60/273,177, filed Mar. 2,2001, Ser. No. 60/273,178, filed Mar. 2, 2001, Ser. No. 60/273,902,filed Mar. 6, 2001, and Ser. No. 60/275,594, filed Mar. 13, 2001; andSer. No. 11/098,984 is also a continuation of Ser. No. 10/052,806, filedJan. 16, 2002, issuing as U.S. Pat. No. 6,880,440 on Apr. 19, 2005,which in turn claimed the benefit of and priority from the followingU.S. Provisional Patent Applications: Ser. No. 60/270,011, filed Feb.20, 2001, Ser. No. 60/270,941, filed Feb. 22, 2001, and Serial No.60/270,942, filed Feb. 22, 2001; and Ser. No. 11/098,984 is also acontinuation of Ser. No. 10/643,296, filed Aug. 18, 2003, and Ser. No.10/932,339, filed Sep. 1, 2004.

FIELD

The present disclosure relates to safety systems and more particularlyto methods for enhancing the safety of power equipment.

BACKGROUND

Power equipment such as table saws, miter saws and other woodworkingmachinery include cutting tools like circular saw blades and knifeblades that present a risk of injury to a user of the equipment.Accordingly, safety features or systems are incorporated with powerequipment to minimize the risk of injury. Probably the most commonsafety feature is a guard that physically blocks an operator from makingcontact with dangerous components of machinery, such as belts, shafts orblades. In many cases, guards effectively reduce the risk of injury,however, there are many instances where the nature of the operations tobe performed precludes using a guard that completely blocks access tohazardous machine parts.

Other safety systems try to prevent or minimize injury by detecting andreacting to an event. For instance, U.S. Pat. Nos. 3,953,770, 4,075,961,4,470,046, 4,532,501 and 5,212,621, the disclosures of which areincorporated herein by reference, disclose radio-frequency safetysystems which utilize radio-frequency signals to detect the presence ofa user's hand in a dangerous area of the machine and thereupon preventor interrupt operation of the machine. U.S. Pat. Nos. 3,785,230 and4,026,177, the disclosures of which are herein incorporated byreference, disclose a safety system for use on circular saws to stop theblade when a user's hand approaches the blade. The system uses the bladeas an antenna in an electromagnetic proximity detector to detect theapproach of a user's hand prior to actual contact with the blade. Upondetection of a user's hand, the system engages a brake using a standardsolenoid.

U.S. Pat. No. 4,117,752, which is herein incorporated by reference,discloses a braking system for use with a band saw, where the brake istriggered by actual contact between the user's hand and the blade.However, the system described for detecting blade contact does notappear to be functional to accurately and reliably detect contact.Furthermore, the system relies on standard electromagnetic brakesoperating off of line voltage to stop the blade and pulleys of the bandsaw. It is believed that such brakes would take 50 ms-1 s to stop theblade. Therefore, the system is too slow to stop the blade quicklyenough to avoid serious injury.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a machine with a fast-actingsafety system.

FIG. 2 is a schematic diagram of an exemplary safety system in thecontext of a machine having a circular blade.

FIG. 3 is a schematic side view of a table saw with a retraction system.

FIG. 4 is a schematic side view of a second side of a table saw with aretraction system.

FIG. 5 is a schematic, side view of a saw with another embodiment of aretraction system.

FIG. 6 is a section view of a retraction system using a deformablebushing.

FIG. 7 is a schematic side view of a miter saw with a retraction system.

FIG. 8 is a section view of the miter saw shown in FIG. 7.

FIG. 9 shows another embodiment of a miter saw with a retraction system.

FIG. 10 shows a schematic drawing of a retraction system using a springto retract a cutting tool.

FIG. 11 is a sectional view of the retraction system shown in FIG. 10.

FIG. 12 also is a sectional view of the retraction system shown in FIG.10.

FIG. 13 is a schematic view of a band saw with a retraction system.

FIG. 14 is a top view of a roller used in the system shown in FIG. 13.

FIG. 15 shows an explosive charge that can be triggered by a firingsubsystem.

DETAILED DESCRIPTION

A machine that may incorporate a retraction system according to thepresent disclosure is shown schematically in FIG. 1 and indicatedgenerally at 10. Machine 10 may be any of a variety of differentmachines adapted for cutting workpieces, such as wood, including a tablesaw, miter saw (chop saw), radial arm saw, circular saw, band saw,jointer, planer, etc. Machine 10 includes an operative structure 12having a cutting tool 14 and a motor assembly 16 adapted to drive thecutting tool. Machine 10 also includes a safety system 18 configured tominimize the potential of a serious injury to a person using machine 10.Safety system 18 is adapted to detect the occurrence of one or moredangerous conditions during use of machine 10. If such a dangerouscondition is detected, safety system 18 is adapted to engage operativestructure 12 to limit any injury to the user caused by the dangerouscondition.

Machine 10 also includes a suitable power source 20 to provide power tooperative structure 12 and safety system 18. Power source 20 may be anexternal power source such as line current, or an internal power sourcesuch as a battery. Alternatively, power source 20 may include acombination of both external and internal power sources. Furthermore,power source 20 may include two or more separate power sources, eachadapted to power different portions of machine 10.

It will be appreciated that operative structure 12 may take any one ofmany different forms, depending on the type of machine 10. For example,operative structure 12 may include a stationary housing configured tosupport motor assembly 16 in driving engagement with cutting tool 14.Alternatively, operative structure 12 may include a movable structureconfigured to carry cutting tool 14 between multiple operatingpositions. As a further alternative, operative structure 12 may includeone or more transport mechanisms adapted to convey a workpiece towardand/or away from cutting tool 14.

Motor assembly 16 includes one or more motors adapted to drive cuttingtool 14. The motors may be either directly or indirectly coupled to thecutting tool, and may also be adapted to drive workpiece transportmechanisms. Cutting tool 14 typically includes one or more blades orother suitable cutting implements that are adapted to cut or removeportions from the workpieces. The particular form of cutting tool 14will vary depending upon the various embodiments of machine 10. Forexample, in table saws, miter saws, circular saws and radial arm saws,cutting tool 14 will typically include one or more circular rotatingblades having a plurality of teeth disposed along the perimetrical edgeof the blade. For a jointer or planer, the cutting tool typicallyincludes a plurality of radially spaced-apart blades. For a band saw,the cutting tool includes an elongate, circuitous tooth-edged band.

Safety system 18 includes a detection subsystem 22, a reaction subsystem24 and a control subsystem 26. Control subsystem 26 may be adapted toreceive inputs from a variety of sources including detection subsystem22, reaction subsystem 24, operative structure 12 and motor assembly 16.The control subsystem may also include one or more sensors adapted tomonitor selected parameters of machine 10. In addition, controlsubsystem 26 typically includes one or more instruments operable by auser to control the machine. The control subsystem is configured tocontrol machine 10 in response to the inputs it receives.

Detection subsystem 22 is configured to detect one or more dangerous, ortriggering, conditions during use of machine 10. For example, thedetection subsystem may be configured to detect that a portion of theuser's body is dangerously close to, or in contact with, a portion ofcutting tool 14. As another example, the detection subsystem may beconfigured to detect the rapid movement of a workpiece due to kickbackby the cutting tool, as is described in U.S. Provisional PatentApplication Ser. Nos. 60/182,866, the disclosure of which is hereinincorporated by reference. In some embodiments, detection subsystem 22may inform control subsystem 26 of the dangerous condition, which thenactivates reaction subsystem 24. In other embodiments, the detectionsubsystem may be adapted to activate the reaction subsystem directly.

Once activated in response to a dangerous condition, reaction subsystem24 is configured to engage operative structure 12 quickly to preventserious injury to the user. It will be appreciated that the particularaction to be taken by reaction subsystem 24 will vary depending on thetype of machine 10 and/or the dangerous condition that is detected. Forexample, reaction subsystem 24 may be configured to do one or more ofthe following: stop the movement of cutting tool 14, disconnect motorassembly 16 from power source 20, place a barrier between the cuttingtool and the user, or retract the cutting tool from its operatingposition, etc. The reaction subsystem may be configured to take acombination of steps to protect the user from serious injury. Placementof a barrier between the cutting tool and teeth is described in moredetail in U.S. Provisional Patent Application Ser. No. 60/225,206,entitled “Cutting Tool Safety System,” filed Aug. 14, 2000 by SD3, LLC,the disclosure of which is herein incorporated by reference.

The configuration of reaction subsystem 24 typically will vary dependingon which action(s) are taken. In the exemplary embodiment depicted inFIG. 1, reaction subsystem 24 is configured to stop the movement ofcutting tool 14 and includes a brake mechanism 28, a biasing mechanism30, a restraining mechanism 32, and a release mechanism 34. Brakemechanism 28 is adapted to engage operative structure 12 under theurging of biasing mechanism 30. During normal operation of machine 10,restraining mechanism 32 holds the brake mechanism out of engagementwith the operative structure. However, upon receipt of an activationsignal by reaction subsystem 24, the brake mechanism is released fromthe restraining mechanism by release mechanism 34, whereupon, the brakemechanism quickly engages at least a portion of the operative structureto bring the cutting tool to a stop.

It will be appreciated by those of skill in the art that the exemplaryembodiment depicted in FIG. 1 and described above may be implemented ina variety of ways depending on the type and configuration of operativestructure 12. Turning attention to FIG. 2, one example of the manypossible implementations of safety system 18 is shown. System 18 isconfigured to engage an operative structure having a cutting tool in theform of a circular blade 40 mounted on a rotating shaft or arbor 42.Blade 40 includes a plurality of cutting teeth (not shown) disposedaround the outer edge of the blade. As described in more detail below,braking mechanism 28 is adapted to engage the teeth of blade 40 and stopthe rotation of the blade. U.S. Provisional Patent Application Ser. No.60/225,210, entitled “Translation Stop For Use In Power Equipment,”filed Aug. 14, 2000 by SD3, LLC, the disclosure of which is hereinincorporated by reference, describes other systems for stopping themovement of the cutting tool. U.S. Provisional Patent Application Ser.No. 60/225,058, entitled “Table Saw With Improved Safety System,” filedAug. 14, 2000 by SD3, LLC, and U.S. Provisional Patent Application Ser.No. 60/225,057, entitled “Miter Saw With Improved Safety System,” filedAug. 14, 2000 by SD3, LLC, the disclosures of which are hereinincorporated by reference, describe safety system 18 in the context ofparticular types of machines 10.

In the exemplary implementation, detection subsystem 22 is adapted todetect the dangerous condition of the user coming into contact withblade 40. The detection subsystem includes a sensor assembly, such ascontact detection plates 44 and 46, capacitively coupled to blade 40 todetect any contact between the user's body and the blade. Typically, theblade, or some larger portion of cutting tool 14 is electricallyisolated from the remainder of machine 10. Alternatively, detectionsubsystem 22 may include a different sensor assembly configured todetect contact in other ways, such as optically, resistively, etc. Inany event, the detection subsystem is adapted to transmit a signal tocontrol subsystem 26 when contact between the user and the blade isdetected. Various exemplary embodiments and implementations of detectionsubsystem 22 are described in more detail in U.S. Provisional PatentApplication Ser. No. 60/225,200, entitled “Contact Detection System ForPower Equipment,” filed Aug. 14, 2000 by SD3, LLC, and U.S. ProvisionalPatent Application Ser. No. 60/225,211, entitled “Apparatus And MethodFor Detecting Dangerous Conditions In Power Equipment,” filed Aug. 14,2000 by SD3, LLC, the disclosures of which are herein incorporated byreference.

Control subsystem 26 includes one or more instruments 48 that areoperable by a user to control the motion of blade 40. Instruments 48 mayinclude start/stop switches, speed controls, direction controls, etc.Control subsystem 26 also includes a logic controller 50 connected toreceive the user's inputs via instruments 48. Logic controller 50 isalso connected to receive a contact detection signal from detectionsubsystem 22. Further, the logic controller may be configured to receiveinputs from other sources (not shown) such as blade motion sensors,workpiece sensors, etc. In any event, the logic controller is configuredto control operative structure 12 in response to the user's inputsthrough instruments 48. However, upon receipt of a contact detectionsignal from detection subsystem 22, the logic controller overrides thecontrol inputs from the user and activates reaction subsystem 24 to stopthe motion of the blade. Various exemplary embodiments andimplementations of control subsystem 26 are described in more detail inU.S. Provisional Patent Application Ser. No. 60/225,059, entitled “LogicControl For Fast Acting Safety System,” filed Aug. 14, 2000 by SD3, LLC,and U.S. Provisional Patent Application Ser. No. 60/225,094, entitled“Motion Detecting System For Use In Safety System For Power Equipment,”filed Aug. 14, 2000 by SD3, LLC, the disclosures of which are hereinincorporated by reference.

In the exemplary implementation, brake mechanism 28 includes a pawl 60mounted adjacent the edge of blade 40 and selectively moveable to engageand grip the teeth of the blade. Pawl 60 may be constructed of anysuitable material adapted to engage and stop the blade. As one example,the pawl may be constructed of a relatively high strength thermoplasticmaterial such as polycarbonate, ultrahigh molecular weight polyethylene(UHMW) or Acrylonitrile Butadiene Styrene (ABS), etc., or a metal suchas aluminum, etc. It will be appreciated that the construction of pawl60 will vary depending on the configuration of blade 40. In any event,the pawl is urged into the blade by a biasing mechanism in the form of aspring 66. In the illustrative embodiment shown in FIG. 2, pawl 60 ispivoted into the teeth of blade 40. It should be understood that slidingor rotary movement of pawl 60 might also be used. The spring is adaptedto urge pawl 60 into the teeth of the blade with sufficient force togrip the blade and quickly bring it to a stop.

The pawl is held away from the edge of the blade by a restrainingmechanism in the form of a fusible member 70. The fusible member isconstructed of a suitable material adapted to restrain the pawl againstthe bias of spring 66, and also adapted to melt under a determinedelectrical current density. Examples of suitable materials for fusiblemember 70 include NiChrome wire, stainless steel wire, etc. The fusiblemember is connected between the pawl and a contact mount 72. Preferably,fusible member 70 holds the pawl relatively close to the edge of theblade to reduce the distance the pawl must travel to engage the blade.Positioning the pawl relatively close to the edge of the blade reducesthe time required for the pawl to engage and stop the blade. Typically,the pawl is held approximately 1/32-inch to ¼-inch from the edge of theblade by fusible member 70, however other pawl-to-blade spacings mayalso be used within the scope of the invention.

Pawl 60 is released from its unactuated, or cocked, position to engageblade 40 by a release mechanism in the form of a firing subsystem 76.The firing subsystem is coupled to contact mount 72, and is configuredto melt fusible member 70 by passing a surge of electrical currentthrough the fusible member. Firing subsystem 76 is coupled to logiccontroller 50 and activated by a signal from the logic controller. Whenthe logic controller receives a contact detection signal from detectionsubsystem 22, the logic controller sends an activation signal to firingsubsystem 76, which melts fusible member 70, thereby releasing the pawlto stop the blade. Various exemplary embodiments and implementations ofreaction subsystem 24 are described in more detail in U.S. ProvisionalPatent Application Ser. No. 60/225,056, entitled “Firing Subsystem ForUse In Fast Acting Safety System,” filed Aug. 14, 2000 by SD3, LLC, U.S.Provisional Patent Application Ser. No. 60/225,170, entitled“Spring-Biased Brake Mechanism for Power Equipment,” filed Aug. 14, 2000by SD3, LLC, and U.S. Provisional Patent Application Ser. No.60/225,169, entitled “Brake Mechanism For Power Equipment,” filed Aug.14, 2000 by SD3, LLC, the disclosures of which are herein incorporatedby reference.

Other systems can also be used to shift the pawl or pawls into contactwith the blade, and firing system 76 may also be used to trigger someaction other than burning a fusible member. For example, firing system76 can fire a small explosive charge to move a pawl. FIG. 15 shows arelatively small, self-contained explosive charge 660 in the form of asquib or detonator that can be used to drive pawl 60 against a blade. Anexample of a suitable explosive charge is an M-100 detonator available,for example, from Stresau Laboratory, Inc., of Spooner, Wis. Althoughany suitable explosive charge system may be used, the exemplaryembodiment preferably uses a self-contained charge or squib to increasesafety and focus the force of the explosion along the direction ofmovement of the pawl. A trigger line 662 extends from the charge, and itmay be connected to firing system 76 to trigger detonation.

Explosive charge 660 can be used to move pawl 60 by inserting the chargebetween the pawl and a stationary block 664 adjacent the charge. Whenthe charge detonates, the pawl is pushed away from the block. Acompression spring 66 is placed between the block and pawl to ensure thepawl does not bounce back from the blade when the charge is detonated.Prior to detonation, the pawl is held away from the blade by thefriction-fit of the charge in both the block and pawl. However, theforce created upon detonation of the charge is more than sufficient toovercome the friction fit. Alternatively, the pawl may be held away fromthe blade by other mechanisms such as a frangible member, gravity, aspring between the pawl and block, etc.

Firing system 76 may also trigger a DC solenoid, which can beover-driven with a current surge to create a rapid displacement, apressurized air or gas cylinder to supply the pressure in place of thespring or charge, or an electromagnet to either repel the pawl againstthe blade or to release a spring-loaded pawl toward the blade.

It will be appreciated that activation of the brake mechanism willrequire the replacement of one or more portions of safety system 18. Forexample, pawl 60 and fusible member 70 typically must be replaced beforethe safety system is ready to be used again. Thus, it may be desirableto construct one or more portions of safety system 18 in a cartridgethat can be easily replaced. For example, in the exemplaryimplementation depicted in FIG. 2, safety system 18 includes areplaceable cartridge 80 having a housing 82. Pawl 60, spring 66,fusible member 70 and contact mount 72 are all mounted within housing82. Alternatively, other portions of safety system 18 may be mountedwithin the housing. In any event, after the reaction system has beenactivated, the safety system can be reset by replacing cartridge 80. Theportions of safety system 18 not mounted within the cartridge may bereplaced separately or reused as appropriate. Various exemplaryembodiments and implementations of a safety system using a replaceablecartridge are described in more detail in U.S. Provisional PatentApplication Ser. No. 60/225,201, entitled “replaceable Brake MechanismFor Power Equipment,” filed Aug. 14, 2000 by SD3, LLC, and U.S.Provisional Patent Application Ser. No. 60/225,212, entitled “BrakePositioning System,” filed Aug. 14, 2000 by SD3, LLC, the disclosures ofwhich are herein incorporated by reference.

While one particular implementation of safety system 18 has beendescribed, it will be appreciated that many variations and modificationsare possible within the scope of the invention. Many such variations andmodifications are described in U.S. Provisional Patent Application Ser.Nos. 60/182,866 and 60/157,340, the disclosures of which are hereinincorporated by reference.

As briefly mentioned above, reaction subsystem 24 can be configured witha retraction system to retract or move a cutting tool away from thepoint of accidental contact with a user. Moving away from the point ofaccidental contact reduces the time the cutting tool is in contact withthe user, thereby minimizing any injury to the user. Moving the cuttingtool away from the point of accidental contact also prevents the cuttingtool from moving toward the user, which could increase any injury to theuser. For example, a spinning blade in a miter saw has substantialangular momentum, and that angular momentum could cause the blade tomove downward toward a user when a brake pawl hits the blade. Thespinning blade in a table saw also has substantial angular momentum thatcould cause the blade to move upward toward a user when a brake pawlhits the blade, depending on the position of the brake, the weight ofthe blade and the amount of play in the structure supporting the blade.Preventing any such movement lessens the potential injury to the user. Aretraction system may be used in addition to or instead of other safetymechanisms.

FIGS. 3 and 4 show side views of a table saw configured with both aretraction system and a braking mechanism. A blade 300 is mounted on anarbor 301 to spin in the direction of arrow 302. A table 303 (not shownin FIG. 4), which defines the work surface or cutting region for thetable saw, is adjacent the blade and the blade extends above the table.A support structure 304 may support blade 300 and arbor 301 in any knownway, or as described in more detail in U.S. Provisional PatentApplication Ser. No. 60/225,058, titled “Table Saw with Improved SafetySystem,” filed Aug. 14, 2000.

Blade 300 is configured to pivot up and down so that a user can positionthe blade to extend above the table as needed. The blade pivots around apin 305. A user may pivot the blade to adjust its position by turning ashaft 306 on which a worm gear 307 is mounted. The worm gear is mountedon the shaft so that it turns with the shaft, but so that it may slideon the shaft when necessary, as explained below. Worm gear 307 ismounted on shaft 306 like a collar, with the shaft extending through alongitudinal hole in the worm gear. The worm gear is held in placeduring normal operation of the saw by a spring clip 308, which ispositioned in a groove or channel 309 on the worm gear and which alsoengages a detent or shoulder on shaft 306 to hold the worm gear inplace. The worm gear engages an arcuate rack 310 that supports an arborblock 311, which in turn supports arbor 301 and blade 300. Thus, when auser turns shaft 306, such as by turning a knob attached to the shaft(not shown), worm gear 307 moves arbor block 311 and the blade up ordown, depending on the direction that the worm gear is turned.

A brake cartridge 312 is mounted in the saw adjacent blade 300. Thebrake cartridge includes a pawl 314 biased toward blade 300 by a spring316. The pawl is held away from blade 300 by a release mechanism 318, asdescribed generally above and as described in more detail in U.S.Provisional Patent Application Ser. No. 60/225,170, entitled“Spring-Biased Brake Mechanism for Power Equipment,” U.S. ProvisionalPatent Application Ser. No. 60/225,169, entitled “Brake Mechanism forPower Equipment,” U.S. Provisional Patent Application Ser. No.60/225,201, entitled “Replaceable Brake Mechanism for Power Equipment,”and U.S. Provisional Patent Application Ser. No. 60/225,212, entitled“Brake Positioning System,” all filed Aug. 14, 2000. The cartridge isconfigured so that the release mechanism releases the pawl into theblade upon the receipt of a detection signal, as explained generallyabove and as explained in more detail in U.S. Provisional PatentApplication Ser. No. 60/225,056, titled “Firing Subsystem for use in aFast-Acting Safety System,” filed Aug. 14, 2000.

Brake cartridge 312 is positioned on the blade's pivot axis so that pawl314 can move around pin 305. Thus, when pawl 314 hits the blade, theangular momentum of the blade is transferred to the arbor block, and theblade, arbor block, rack and cartridge try to retract or move down inthe direction of arrow 320. Alternatively, the cartridge may bepositioned on a pin different from pin 305, but that still pivots withthe blade.

The blade will move down to the extent permitted by the contact betweenrack 310 and worm gear 307. If the worm gear is fixed in place, thedownward movement of the blade may strip teeth on the rack and/or wormgear, and may prevent the blade from moving down as far as desired. Inthe embodiment shown in FIGS. 3 and 4, the worm gear is adapted to snapfree and move on shaft 306 when the pawl hits the blade.

When the pawl hits the blade, the resultant angular momentum impulsecauses spring clip 308 to snap loose, allowing the worm gear to slidedown the shaft toward an end 322 of the shaft. The spring clip snapsloose because the rack moves down when the blade is stopped, and therack contacts the worm gear and forces the worm gear to move. The forceof the rack against the worm gear causes the spring clip to snap loose.The worm gear is put back in place by moving it back along shaft 306until the spring clip snaps into place on the shaft.

The table saw shown in FIGS. 3 and 4 also includes a support 326configured with a seat or region 328 in which is placed animpact-absorbing material 330. The support is positioned under the arborand arbor block so that when the blade retracts, the arbor block strikesimpact-absorbing material 330. Support 326 and impact absorbing material330 act as a barrier to stop the downward movement of the blade. Thesupport is positioned so that blade 300 may retract a sufficientdistance. The impact-absorbing material can be any one of a number ofcushioning materials, such as rubber, dense foam, plastic, etc. Onematerial found to be suitable is available under the part numberC-1002-06 from AearoEAR, of Indianapolis, Ind. Alternatively,impact-absorbing material 330 may be attached to the undersurface of thearbor block instead of on support 326. Additionally, support 326 maytake many forms. In fact, shaft 306 may be configured and positioned sothat it provides a surface to stop the downward movement of the blade.

FIG. 4 also shows a splitter 335 that extends above table 303 behindblade 300 to prevent kickback. A blade guard may also substantiallyenclose blade 300. FIG. 4 further shows a housing 337 for electroniccomponents relating to the safety system, and a motor mount 339, whichare not shown in FIG. 3.

In the construction described above, the angular momentum of the bladecauses the blade, arbor block and cartridge to all pivot down away fromthe cutting region when the pawl strikes the blade. Thus, the angularmomentum of the blade causes the retraction. Blade 300 is permitted tomove downward a sufficient distance so that the blade is completelyretracted. In independent experiments, the safety system depicted inFIGS. 3 and 4 and described above has been shown to retract the bladecompletely below table 303 within approximately 14 milliseconds aftercontact is detected. Indeed the downward motion of the blade duringretraction is too fast to detect with the human eye, i.e., the bladedisappears below table 303 with no discernable transition or downwardmotion. The ability of the blade to retract minimizes any injury fromaccidental contact with the blade.

FIG. 5 shows another embodiment of a retraction system used with a brakepawl. A saw 331 includes a blade 300 and a brake cartridge 312 housing abrake pawl 314. The cartridge and pawl are mounted to the frame of thesaw by a pin 332. The pin is mounted to the saw in such a way that itmay not pivot up and down with the blade. When the blade hits the pawl,the blade climbs down the pawl or in other words, moves generally aroundthe point of contact with the pawl. The pawl and blade do not pivotdownward together, as in the embodiment shown in FIGS. 3 and 4, becausethe pawl is fixed to the frame of the saw. In this embodiment, the bladeretracts by “climbing” down the pawl.

Another embodiment of a retraction system comprises a compressiblebushing. Typically, a blade 300 in a table saw, miter saw or othermachine is mounted to an arbor over a bushing 333, as shown in FIG. 6. Alocking nut, washers and an arbor flange are used to secure the blade tothe arbor. Bushing 333 may be constructed from a material that is softenough to deform when the blade is stopped suddenly. For example,depending on the type of braking system used, a substantial radialimpact load may be transmitted to the arbor when the brake is actuated.A deformable bushing can be used to absorb some of this impact andreduce the chance of damage to the arbor. In addition, properpositioning of the brake in combination with a deformable bushing may beemployed to cause the blade to move away from the user upon activationof the brake. Where a plastic bushing is placed between the blade andthe arbor, the substantial force created by stopping the blade almostinstantly may cause the bushing to deform. Typically, the edge of themounting hole of the blade will bite into the bushing as the bladeattempts to rotate about the pawl. Therefore, if the pawl is mounted atthe back of the blade, then the blade will tend to move downward intothe bushing and away from the user when the pawl engages the blade.

FIGS. 7 and 8 show a miter saw equipped with both a brake and aretraction system.

The miter saw is configured with a pivotal motor assembly to allow theblade to move upward into the housing upon engagement with a brake pawl348. Motor assembly 350 is connected to housing 352 via pivot bolt 354,allowing the motor assembly to pivot about bolt 354 in the direction ofblade rotation. A spring 356 is compressed between the motor assemblyand an anchor 358 to bias the motor assembly against the direction ofblade rotation. The motor assembly may include a lip 360, which slidesagainst a flange 362 on the housing to hold the end of the motorassembly opposite the pivot bolt against the housing.

When the saw is in use, spring 356 holds the motor assembly in a normalposition rotated fully counter to the direction of blade rotation.However, once the pawl is released to engage the blade, the motorassembly and blade pivot upward against the bias of the spring. In thisembodiment, the pawl is positioned at the front of the blade so that thepivot bolt 354 is between the pawl and the arbor. This arrangementencourages the blade to move upward into the housing when stopped. Thespring is selected to be sufficiently strong to hold the motor assemblydown when cutting through a workpiece, but sufficiently compressible toallow the blade and motor assembly to move upward when the blade isstopped. Of course, the blade and motor assembly may be configured inany of a variety of ways to at least partially absorb the angularmomentum of the blade.

FIG. 9 shows an alternative configuration of a miter saw adapted to moveaway from an accidental contact with a user by absorbing the angularmomentum of the blade. In this configuration, the miter saw includes twoswing arms 370 and 372. One end 374 of each swing arm 370, 372 isconnected to base 376, and the opposite end 378 of each swing arm isconnected to housing 380, the blade, and/or the motor assembly (notshown). The position of the swing arms relative to each other may varydepending on the swing arm motion desired. In FIG. 9, swing arm 370 isconnected to base 376 somewhat below and forward of swing arm 372.Typically, the motor assembly is rigidly attached to end 378 of swingarm 370, while housing 380 is connected to rotate about end 378 of swingarm 370. End 378 of swing arm 372 is connected only to the housing.Alternatively, the motor assembly may be connected to rotate about end378 of swing arm 370 along with the housing.

The geometry of the configuration shown in FIG. 9 causes the housingand/or motor assembly to rotate as the swing arms pivot. Significantly,when the swing arms move upward, the housing and/or motor assemblyrotate in the same direction in which the blade rotates during cutting.As a result, when a brake pawl engages the blade and transfers theangular momentum of the blade to the housing and/or motor assembly, thehousing and/or motor assembly tend to rotate in the same direction asthe blade. This causes the swing arms to pivot upward, drawing the bladeaway from the workpiece and the user's body. Thus, the miter sawconfiguration illustrated in FIG. 9 is adapted to absorb the angularmomentum of the blade and translate that angular momentum into an upwardforce on the swing arms.

In any of the systems described above, a spring or other force can beused to push the blade away from the point of contact with the user. Thespring could be released by a mechanism similar to the mechanism thatreleases the pawl to strike the blade. FIGS. 10-12 show how a spring maybe used to retract a blade in a table saw. FIG. 10 is a top view andFIGS. 11 and 12 are side views of an arbor block 381 holding an arbor382 used to drive a blade (not shown). Arbor block 381 is pivotallymounted to pin 383 so that the arbor block and blade may pivot up anddown to adjust the position of the blade in the saw.

A segment gear 384, like rack 310 described above in connection withFIGS. 3 and 4, is also mounted on pin 383, and is connected to arborblock 381 in the manner described below, to raise and lower the arbor.Segment gear 384 includes a side portion 385 positioned substantiallyperpendicularly to the plane of arbor block 381, and a top portion 386positioned over arbor block 381. The side portion 385 includes gearteeth 387 to engage a worm gear to raise and lower the arbor block. Sideportion 385 and top portion 386 are connected to each other and movetogether. Top portion 386 extends over the top of the entire arborblock, as shown. The arbor block is constructed with a region toaccommodate top portion 386 so that top portion 386 does not extendsubstantially above the arbor block, which could limit the ability ofthe arbor block and blade to pivot upward when desired, such as bycontacting the underside of a table in a table saw.

A pocket 388 is formed in arbor block 381 to house a spring 389. In theposition shown in FIG. 11, spring 389 is compressed between top portion386 of segment gear 384 and arbor block 381 because the segment gear andarbor block are coupled together.

The segment gear and arbor block are coupled by a compound linkagehaving, as shown in FIG. 12, a first arm 390 attached at one end to thearbor block and at its other end to a second arm 391. The second arm, inturn, is attached to top portion 386 of segment gear 384, as shown.First and second arms 390 and 391 are hingedly connected to each other,and to the arbor block and segment gear. The arms are configured so thatthe force of the spring pushing apart the arbor block and the topportion of the segment gear biases the first and second arms in such away that the arms want to move. A fusible member 392, which may take theform of a wire as described above, restrains the arms from movement. Ofcourse, numerous different linkages may be used, and numerous types andconfigurations of fusible members or other release mechanisms may beused. The linkage may be selected to provide a sufficient mechanicaladvantage so that the arbor block and top portion of the segment gearmay be held together with as thin a fusible member as possible, so thatthe fusible member may be burned as easily as possible. Variousanalogous compound linkages are described in U.S. Provisional PatentApplication Ser. No. 60/225,170, entitled “Spring-Biased Brake Mechanismfor Power Equipment,” filed Aug. 14, 2000. The fusible member may beburned by a system as described above, or as described in more detail inU.S. Provisional Patent Application Ser. No. 60/225,056, entitled“Firing Subsystem for Use in Fast-Acting Safety System,” filed Aug. 14,2000, the disclosure of which is hereby incorporated by reference. Thecompound linkage and the fusible member are preferably configured sothat they accommodate spring forces of 100 to 500 pounds or more. Inother embodiments, the restraining member may include various mechanicallinkages, or may be part of various actuators, and those linkages and/oractuators may be released or fired by solenoids, gas cylinders,electromagnets, and/or explosives, as explained in U.S. ProvisionalPatent Application Ser. No. 60/302,916, entitled “Actuators for Use inFast-Acting Safety Systems,” filed Jul. 3, 2001, the disclosure of whichis hereby incorporated by reference.

When the fusible member is burned, the compound linkage is free to move,and the spring pushes arbor block 381 down, away from top portion 386 ofthe segment gear, as shown by the dashed lines in FIG. 11, therebyretracting the blade. The stronger the spring, the faster the blade willbe retracted. The segment gear does not move because it is coupledthrough teeth 387 to a worm gear or some other structure.

Retracting a blade by a spring or some other force may be thought of asdirect retraction. A spring or other force may be used with some otherretraction system to increase the speed that a cutting tool retracts, ora spring or other force may be used as the sole means of retraction. Thesystems for direct retraction described above may be used on variouspieces of equipment, including table saws, miter saws and band saws.

FIG. 13 is a schematic diagram of a system to retract the blade of aband saw. Typically, a band saw includes a main housing enclosing a pairof vertically spaced-apart wheels. The perimeter of each wheel is coatedor covered in a high-friction material such as rubber, etc. A relativelythin, continuous loop blade tightly encircles both wheels. A workpieceis cut by passing it toward the blade in a cutting zone between thewheels. The workpiece is passed toward the blade on a table, which formsthe bottom of the cutting zone.

The band saw shown in FIG. 13 includes roller 393 positioned adjacentthe blade. The roller is configured to contact the blade and push theblade away from the point of accidental contact with a user. Inaddition, the roller may be configured to push the blade off the wheels,thereby stopping the motion of the blade. A top view of the roller isshown in FIG. 14 pushing against a blade in the direction of the arrow.The roller may be part of a cartridge, and may be released into theblade just as the pawls described above are released. The roller shouldhave a diameter large enough so that the roller can roll over the teethof the blade.

The systems for direct retraction of a cutting tool may also beimplemented on hand-held circular saws. Such saws typically include abase plate that contacts a workpiece during sawing. The base platesupports the saw on the workpiece. The base plate may be configured sothat it is pushed down when the blade contacts a user. The result ofthat action is to effectively retract the blade because the base platewould push the user away from the blade.

INDUSTRIAL APPLICABILITY

The present invention is applicable to power equipment, and specificallyto woodworking equipment such as table saws, miter saws, band saws,circular saws, jointers, etc. The present invention provides a safetysystem wherein a cutting tool or other dangerous item is retracted uponthe occurrence of a specified event, such as when accidental contactbetween a user and a blade is detected. Retraction of a cutting tool,for example, can minimize any injury from accidental contact with thecutting tool by reducing the amount of time the cutting tool is incontact with a user or by moving the cutting tool to a position wherethe user cannot contact it. A retraction system may be used incombination with other safety features to maximize the performance of anoverall safety system. For example, a retraction system may be used witha system that quickly stops a cutting tool so that the cutting toolsimultaneously stops and moves away from a user.

It is believed that the disclosure set forth above encompasses multipledistinct inventions with independent utility. While each of theseinventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Thesubject matter of the inventions includes all novel and non-obviouscombinations and subcombinations of the various elements, features,functions and/or properties disclosed herein. No single feature,function, element or property of the disclosed embodiments is essentialto all of the disclosed inventions. Similarly, where the claims recite“a” or “a first” element or the equivalent thereof, such claims shouldbe understood to include incorporation of one or more such elements,neither requiring nor excluding two or more such elements.

It is believed that the following claims particularly point out certaincombinations and subcombinations that are directed to one of thedisclosed inventions and are novel and non-obvious. Inventions embodiedin other combinations and subcombinations of features, functions,elements and/or properties may be claimed through amendment of thepresent claims or presentation of new claims in this or a relatedapplication. Such amended or new claims, whether they are directed to adifferent invention or directed to the same invention, whetherdifferent, broader, narrower or equal in scope to the original claims,are also regarded as included within the subject matter of theinventions of the present disclosure.

1. A cutting machine comprising: a blade configured to cut a workpiece;a detection system configured to detect a dangerous condition; areaction system adapted to perform a specified action to mitigatepossible injury from the dangerous condition; and an explosive totrigger the reaction system to perform the specified action when fired.2. The cutting machine of claim 1, where the blade moves to cut aworkpiece, and where the specified action is to stop the blade.
 3. Thecutting machine of claim 1, where the specified action is to cover theblade.
 4. The cutting machine of claim 1, where the blade is configuredto cut a workpiece in a work zone, and where the specified action is toretract the blade at least partially away from the workzone.
 5. Thecutting machine of claim 1, where the dangerous condition is contactbetween a person and the blade.
 6. The cutting machine of claim 1, wherethe dangerous condition is proximity between a person and the blade. 7.The cutting machine of claim 1, where the blade is configured to cut aworkpiece in a work zone, where the specified action is to retract theblade at least partially out of the workzone, and where the dangerouscondition is contact between a person and the blade.
 8. The cuttingmachine of claim 1, where the blade is configured to cut a workpiece ina work zone, where the specified action is to retract the blade at leastpartially out of the workzone, and where the dangerous condition isproximity between a person and the blade.
 9. The cutting machine ofclaim 1, where the reaction system is configured so that firing theexplosive causes at least a part of the reaction system to move.
 10. Thecutting machine of claim 1, further comprising a firing subsystem tofire the explosive upon detection of the dangerous condition.
 11. Awoodworking machine having a cutting region for cutting workpieces,comprising: a movable cutting tool for cutting workpieces in the cuttingregion; a detection system adapted to detect a dangerous conditionbetween a person and the cutting tool; and a reaction system associatedwith the detection system and the cutting tool, where the reactionsystem is configured to pivot the cutting tool at least partially awayfrom the cutting region upon detection of the dangerous condition by thedetection system.
 12. The woodworking machine of claim 11 where thedangerous condition is contact between a person and the cutting tool.13. The woodworking machine of claim 11 where the dangerous condition isproximity of a person to the cutting tool.
 14. The woodworking machineof claim 11 further comprising a rotatable arbor on which the cuttingtool is mounted, an arbor block adapted to support the arbor, and asupport structure to which the arbor block is pivotally mounted; andwhere the reaction system is configured to pivot the arbor block, arborand cutting tool at least partially away from the cutting region upondetection of the dangerous condition by the detection system.
 15. Thewoodworking machine of claim 14 where the cutting tool is a circularblade, where the machine is configured to cut a workpiece by moving theworkpiece in a feed direction past the blade, and where the arbor blockis pivotally mounted to the support structure downstream from the bladerelative to the feed direction.
 16. The woodworking machine of claim 14where the cutting tool is a circular blade, where the machine isconfigured to cut a workpiece by moving the workpiece in a feeddirection past the blade, and where the arbor block is mounted to thesupport structure at a pivot point behind the blade relative to the feeddirection.
 17. The woodworking machine of claim 14 where the cuttingtool is a circular blade, where the machine is configured to cut aworkpiece by moving the workpiece in a feed direction past the blade,where the support structure includes a trunnion to which the arbor blockis pivotally mounted, and where the trunnion is positioned behind theblade relative to the feed direction.
 18. A woodworking machinecomprising: a table having a work surface defining a cutting region; acutting tool positioned to extend at least partially into the cuttingregion; a detection system adapted to detect a dangerous conditionbetween a person and the cutting tool; and a reaction system associatedwith the detection system and the cutting tool, where the reactionsystem is configured to retract the cutting tool completely below thework surface within approximately 14 milliseconds after the dangerouscondition is detected by the detection system.
 19. The woodworkingmachine of claim 18 where the dangerous condition is contact between aperson and the cutting tool.
 20. The woodworking machine of claim 18where the dangerous condition is proximity of a person to the cuttingtool.